<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
     content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    #progress{
      width: 300px;
      height: 20px;
      background-color:#f7f7f7;
      box-shadow:inset 0 1px 2px rgba(0,0,0,0.1);
      border-radius:4px;
      background-image:linear-gradient(to bottom,#f5f5f5,#f9f9f9);
    }
 
    #finish{
      background-color: #149bdf;
      background-image:linear-gradient(45deg,rgba(255,255,255,0.15) 25%,transparent 25%,transparent 50%,rgba(255,255,255,0.15) 50%,rgba(255,255,255,0.15) 75%,transparent 75%,transparent);
      background-size:40px 40px;
      height: 100%;
    }
    form{
      margin-top: 50px;
    }
  </style>
</head>
<body>
<div id="progress">
  <div id="finish" style="width: 0%;" progress="0"></div>
</div>
<form action="./upload.php">
  <input type="file" name="file" id="file">
  <input type="button" value="停止" id="stop">
</form>
<script>
  var fileForm = document.getElementById("file");
  var stopBtn = document.getElementById('stop');
  var upload = new Upload();
 
  fileForm.onchange = function(){
    upload.addFileAndSend(this);
  }
 
  stopBtn.onclick = function(){
    this.value = "停止中";
    upload.stop();
    this.value = "已停止";
  }
 
  function Upload(){
    var xhr = new XMLHttpRequest();
    var form_data = new FormData();
    const LENGTH = 1024 * 1024*2;
    var start = 0;
    var end = start + LENGTH;
    var blob;
    var blob_num = 1;
    var is_stop = 0
    //对外方法，传入文件对象
    this.addFileAndSend = function(that){
      var file = that.files[0];
      blob = cutFile(file);
      sendFile(blob,file);
      blob_num += 1;
    }
    //停止文件上传
    this.stop = function(){
      xhr.abort();
      is_stop = 1;
    }
    //切割文件
    function cutFile(file){
      var file_blob = file.slice(start,end);
      start = end;
      end = start + LENGTH;
      return file_blob;
    };
    //发送文件
    function sendFile(blob,file){
      var form_data = new FormData();
      var total_blob_num = Math.ceil(file.size / LENGTH);
      form_data.append('file',blob);
      form_data.append('blob_num',blob_num);
      form_data.append('total_blob_num',total_blob_num);
      form_data.append('file_name',file.name);
 
      xhr.open('POST','./upload.php',false);
      xhr.onreadystatechange = function () {
        var progress;
        var progressObj = document.getElementById('finish');
        if(total_blob_num == 1){
          progress = '100%';
        }else{
          progress = Math.min(100,(blob_num/total_blob_num)* 100 ) +'%';
        }
        progressObj.style.width = progress;
        var t = setTimeout(function(){
          if(start < file.size && is_stop === 0){
            blob = cutFile(file);
            sendFile(blob,file);
            blob_num += 1;
          }else{
            setTimeout(t);
          }
        },1000);
      }
      xhr.send(form_data);
    }
  }
 
</script>
</body>
</html>